Williamson also told reporters there are signs of possible progress in Darfur's long peace process. He said there was a "serious reassessment" on how to energize a peace process in Darfur. He did not give specifics.

Darfur has been torn apart by a five-year conflict between local rebel groups, the government and government-backed militias.

International experts say the conflict has killed as many as 300,000 people and displaced 2.5 million. Sudan says Western governments and the media have exaggerated the conflict.